A conventional package-type quartz resonator is structured such that a quartz crystal blank 11 on whose both main surfaces electrodes 2a, 2b are formed in the same pattern as shown in FIG. 8 is housed in a package 10 which is composed of a ceramic base 12 and a metal cover 13 as shown in FIG. 7. The base 12 and the cover 13 are seam-welded via a sealing member made of, for example, a welding material, and the inside thereof is in a vacuum state.
A method of manufacturing the aforesaid package-type quartz resonator will be briefly described. First, a quartz wafer is prepared in which a plurality of quartz crystal blank 11 which are rectangular as shown in FIG. 8 are arranged in vertical and lateral directions. Subsequently, the quartz wafer is cut along contours of the quartz crystal blank 11 by dicing or the like to be divided into individual pieces. Then, the individually separated quartz crystal blank 11 are placed one by one via a conductive adhesive 15 in a plurality of recessed portions formed in a front surface of the ceramic base. After all the quartz crystal blank 11 are placed on the ceramic base, the cover 16 is bonded on the ceramic base via the sealing member, and the sealing member portion is heated so that the cover 16 is fixed to the front surface of the ceramic base. Thereafter, this stack is cut by dicing or the like along division lines formed on a front surface of the stack, whereby the package-type quartz resonators shown in FIG. 7 are completed.
In the above-described method of manufacturing the package-type quartz resonator, however, since the quartz crystal blank 11 are placed one by one in the recessed portions of the ceramic base after the quartz crystal blank 11 are cut out from the quartz wafer, it takes long time to place all the quartz crystal blank 11 on the ceramic base and hence manufacturing efficiency is low. Further, it is difficult to transport the small quartz crystal blank 11. That is, this method is not suitable for mass production of the package-type quartz resonator.
Further, since the base 12 and the cover 13 are made of different kinds of materials, their difference in thermal expansion coefficient causes a distortion between the base 12 and the cover 13 to lower bonding strength when the cover 13 seals (is joined to) the base 12, which sometimes prevents high airtightness. Further, as shown in FIG. 7, since the quartz crystal blank 11 is fixed on a front surface of a pedestal 16 of the base 12 via the conductive adhesive 15, gas is generated from the conductive adhesive 15 during annealing, and this released gas is filled in the package 10 to fluctuate or deteriorate a characteristic of the quartz crystal blank 11.
Therefore, there has been proposed an art in which a stack is formed by the packaging at the wafer stage where the plural elements are simultaneously formed, and the stack is cut along predetermined lines, whereby packaged elements are produced (see a patent document 1). However, since the whole peripheries of wafers are sealed (joined) by anodic bonding using aluminum (Al) and molybdenum (Mo) at the time of the packaging, there is a problem that electrodes connecting the elements and external terminals cannot be led out via a joint surface. Further, forming through holes on a bottom surface of the stack so as to allow the electrodes to be led out via the through holes is not advisable since this requires a process of sealing the through holes communicating with a space inside the stack and increases the number of processes. Therefore, though being an appropriate method in view of the mass production of the package-type quartz resonator, the patent document 1 gives no consideration to how the electrodes connecting the elements and the external terminals should be led out and how the sealing should be done, in actual mass-produced products.
A patent document 2 describes that a quartz resonator is airtightly sealed in the following manner. First, excitation electrodes are formed on a front and a rear surface of a vibration plate having a vibrating portion in a tongue piece shape, and lead electrodes are led out from the excitation electrodes via a root portion of the vibrating portion. One of the lead electrodes forms a first connection part and the other lead electrode penetrates to the one lead electrode side to thereafter form a second connection part, and a first cover of quartz crystal and having through holes is joined to one surface of the vibration plate. The first and second connection parts are electrically connected via the through holes provided in the first cover to conduction electrodes formed on inner surfaces of the through holes. Subsequently, a second cover of quartz crystal is joined to the other surface of the vibration plate to form a package, and sealing electrodes are formed so as to cover the conduction electrodes formed on the inner surfaces of the through holes of the first cover, so that the package is airtightly sealed.
Further, the vibration plate has a large thickness in its portion sandwiched by the first cover and the second cover, and its portions such as portions where the vibrating portion and the lead electrodes are formed are made small by etching. Consequently, in the state in which the vibration plate is sandwiched by the first cover and the second cover, it is prevented that a gap is formed between the vibration plate and the first cover or the second cover due to the thickness of the lead electrodes formed on the surfaces of the vibration plate. That is, by thus forming the vibration plate, high airtightness of the package-type quartz resonator is realized. However, in fabricating the package-type quartz resonator, this method requires working of the vibration plate to make its portion sandwiched by the first cover and the second cover thick and to make its portions such as the portions where the vibrating portion and the lead electrodes are formed thin, resulting in an increased number of processes for manufacturing the package-type quartz resonator. Further, since the thickness of the portions where the vibrating portion and the lead electrodes are formed are made small, there is also a problem that the vibration plate is easily broken when it is handled.
Patent Document 1
    Japanese Patent Application Laid-open No. 2006-180168 (paragraph 0012 and FIG. 1)Patent Document 2    Japanese Patent Application Laid-open No. Hei 8-335839 (paragraph 0012, FIG. 2, FIG. 3, and FIG. 6)